The invention relates to a two-stage continuous roasting process for coffee in which the roasted coffee product is of low density and high yield.
Green coffee is roasted to produce the desired dark brown color and to alter the natural elements present in the green beans to provide the aromatic qualities and taste or flavor values desired in a freshly brewed coffee beverage. One known technique for the continuous roasting of coffee is disclosed in Nutting et al U.S. Pat. No. 3,572,235. There, the coffee beans are first subjected to steam in a pre-heating zone and thereafter progressively moved as a fluidized bed through a roasting zone in which the pre-heated beans are contacted with a hot roasting gas at a temperature in the range of 450.degree. F.-575.degree. F. Then, the beans are dried by contact with an ambient air stream.
In recent years, the above process has been modified by the elimination of the pre-heating stage and the direct feeding of the green coffee beans into a two-stage roasting zone. In typical operation, the temperature in the first zone is on the order of 475.degree. F. while in the second zone, the temperature is slightly higher, on the order of 485.degree. F. This process (referred to herein as the "prior art process") produces a product of superior flavor, taste and aroma.
It is well known that the price of coffee has increased significantly in recent years. For economy, it would be desirable to increase the yield per volume of green coffee beans assuming that the quality of coffee could be maintained.
It is an object of the invention to provide a continuous roasting process in which the desired flavor and aroma characteristics are developed from the green coffee beans to produce a high yield, low density roasted coffee product.
It is a specific object of the invention to provide a roasting process of the foregoing type capable of forming a roasted coffee product of substantially reduced density and of comparable yield to that of conventional ground roast coffee.
Additional objects and features of the invention will appear from the following detailed description taken in conjunction with the accompanying drawings.